﻿// https://raw.githubusercontent.com/dotnet/samples/master/csharp/roslyn-sdk/Tutorials/MakeConst/MakeConst.Test/Helpers/CodeFixVerifier.Helper.cs

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Simplification;

namespace Ardalis.ApiEndpoints.CodeAnalyzers.Test.Verifiers;

/// <summary>
/// Diagnostic Producer class with extra methods dealing with applying codefixes
/// All methods are static
/// </summary>
public abstract partial class CodeFixVerifier : DiagnosticVerifier
{
  /// <summary>
  /// Apply the inputted CodeAction to the inputted document.
  /// Meant to be used to apply codefixes.
  /// </summary>
  /// <param name="document">The Document to apply the fix on</param>
  /// <param name="codeAction">A CodeAction that will be applied to the Document.</param>
  /// <returns>A Document with the changes from the CodeAction</returns>
  private static Document ApplyFix(Document document, CodeAction codeAction)
  {
    var operations = codeAction.GetOperationsAsync(CancellationToken.None).Result;
    var solution = operations.OfType<ApplyChangesOperation>().Single().ChangedSolution;
    return solution.GetDocument(document.Id);
  }

  /// <summary>
  /// Compare two collections of Diagnostics,and return a list of any new diagnostics that appear only in the second collection.
  /// Note: Considers Diagnostics to be the same if they have the same Ids.  In the case of multiple diagnostics with the same Id in a row,
  /// this method may not necessarily return the new one.
  /// </summary>
  /// <param name="diagnostics">The Diagnostics that existed in the code before the CodeFix was applied</param>
  /// <param name="newDiagnostics">The Diagnostics that exist in the code after the CodeFix was applied</param>
  /// <returns>A list of Diagnostics that only surfaced in the code after the CodeFix was applied</returns>
  private static IEnumerable<Diagnostic> GetNewDiagnostics(IEnumerable<Diagnostic> diagnostics, IEnumerable<Diagnostic> newDiagnostics)
  {
    var oldArray = diagnostics.OrderBy(d => d.Location.SourceSpan.Start).ToArray();
    var newArray = newDiagnostics.OrderBy(d => d.Location.SourceSpan.Start).ToArray();

    int oldIndex = 0;
    int newIndex = 0;

    while (newIndex < newArray.Length)
    {
      if (oldIndex < oldArray.Length && oldArray[oldIndex].Id == newArray[newIndex].Id)
      {
        ++oldIndex;
        ++newIndex;
      }
      else
      {
        yield return newArray[newIndex++];
      }
    }
  }

  /// <summary>
  /// Get the existing compiler diagnostics on the inputted document.
  /// </summary>
  /// <param name="document">The Document to run the compiler diagnostic analyzers on</param>
  /// <returns>The compiler diagnostics that were found in the code</returns>
  private static IEnumerable<Diagnostic> GetCompilerDiagnostics(Document document)
  {
    return document.GetSemanticModelAsync().Result.GetDiagnostics();
  }

  /// <summary>
  /// Given a document, turn it into a string based on the syntax root
  /// </summary>
  /// <param name="document">The Document to be converted to a string</param>
  /// <returns>A string containing the syntax of the Document after formatting</returns>
  private static string GetStringFromDocument(Document document)
  {
    var simplifiedDoc = Simplifier.ReduceAsync(document, Simplifier.Annotation).Result;
    var root = simplifiedDoc.GetSyntaxRootAsync().Result;
    root = Formatter.Format(root, Formatter.Annotation, simplifiedDoc.Project.Solution.Workspace);
    return root.GetText().ToString();
  }
}
